Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there–on a mote of dust suspended in a sunbeam.
Don’t let the name fool you: a black hole is anything but empty space. Rather, it is a great amount of matter packed into a very small area – think of a star ten times more massive than the Sun squeezed into a sphere approximately the diameter of New York City. The result is a gravitational field so strong that nothing, not even light, can escape. In recent years, NASA instruments have painted a new picture of these strange objects that are, to many, the most fascinating objects in space.
Black holes were predicted by Einstein’s theory of general relativity, which showed that when a massive star dies, it leaves behind a small, dense remnant core. If the core’s mass is more than about three times the mass of the Sun, the equations showed, the force of gravity overwhelms all other forces and produces a black hole.
Activity 1: Highlight the most representative events in each step.
This is a video explaining the expansion of the universe, the big bang theory and the meaning of dark matter. Astronomers talk us through what we know and don’t know about the universe.
An eXtreme deep field Hubble image.
This image shows the position of the most distant galaxy discovered so far within a deep sky Hubble Space Telescope survey called GOODS North. The survey field contains tens of thousands of galaxies stretching far back into time.
The remote galaxy GN-z11, shown in the inset, existed only 400 million years after the Big Bang when the universe was only 3 percent of its current age. It belongs to the first generation of galaxies in the universe, and its discovery provides new insights into the early universe. This is the first time that the distance of an object so far away has been measured from its spectrum, which makes the measurement extremely reliable.
GN-z11 is actually ablaze with bright young blue stars, but these look red in this image because its light was stretched to longer, redder wavelengths by the expansion of the universe.
Alice: Would you tell me, please, which way I ought to go from here?
The Cheshire Cat: That depends a good deal on where you want to get to.
Alice: I don’t much care where.
The Cheshire Cat: Then it doesn’t much matter which way you go.
Alice: …So long as I get somewhere.
The Cheshire Cat: Oh, you’re sure to do that, if only you walk long enough.
Alice in Wonderland